Because you have selected to delete at least one array, at least one extent pool is not going to have an array that is assigned to it. The extent pools that are going to be without an assigned array are listed in the message.
Select Yes if you want to delete the arrays and the extent pools that are no longer going to have an assigned array because you have deleted the selected arrays.
Select No if you want to delete only the selected arrays and their corresponding ranks and volumes. The extent pools are not going to be deleted.
Select Cancel if you want cancel the entire operation. If you select Cancel neither, the arrays nor the extent pools are going to be deleted.